1. Field of the Invention
The present invention relates to an image printing data control method for thermal transfer printers, and more particularly to an image printing data control method for thermal transfer printers for controlling printing based on various image printing data including undercoat printing data for carrying out undercoat printing on recording paper, image data for carrying out desired image printing, and overcoat printing data for carrying out overcoat printing with transparent ink over said image printing.
2. Description of the Prior Art
In recent years, in order to carry out satisfactory image printing on recording paper, such as ordinary paper and rough paper with relatively uneven surface, printing methods for thermal transfer printers are proposed by which satisfactory printing results are achieved by performing desired image printing with color ink after conducting undercoat printing by the use of an ink ribbon coated with either white ink or transparent ink to smoothen the surface of the recording paper, and further overcoating the printed surface with transparent ink to improve the weatherability or scratch-resistance of the printed surface.
In such a thermal transfer printer, first a ribbon cassette housing an ink ribbon coated with transparent ink or white ink is mounted on the carriage of the printer, and undercoat printing is accomplished on the basis of printing data transmitted from a host side control section such as an external computer or the like.
Image printing based on image data is performed over the surface of the undercoat-printed area using ordinary magenta, cyan blue and yellow color inks, overcoat printing with transparent ink is further applied over this printed image.
In such a printing process, as illustrated in FIG. 3 (Prior Art), undercoat printing data 4 for undercoat printing, image data 5 for image printing and overcoat printing data 6 for overcoat printing are transmitted in a time series from the aforementioned host side control section.
In the above-described printing process of a thermal transfer printer, the quantity of image data to be stored in an external control section or the like can be reduced by having printing data for undercoat printing and overcoat printing as rectangular area information, but printing data for causing a thermal transfer printer to execute printing and printing instructions therefor need to be transmitted in a time series. Accordingly, although the external control section is transmitting the rectangular area information as image printing data, it has to effect printing control over the thermal transfer printer even after the transmission of the image printing data, causing such problems as a low data processing speed, and that the thermal transfer printer has to go through operating cycles to shift to different steps of printing, i.e. from undercoat printing to image printing and then to overcoat printing, as instructed by external host control means, and accordingly takes a long printing time.